A pump is a device used to move fluids, such as liquids, gases, or slurries. A pump displaces a volume of a fluid by physical or mechanical action. A gear pump is a type of a pump that uses two meshed gears rotating in a closely fitted casing to displace a work fluid. Gear pumps are used to pump a constant amount of fluid for each revolution of the meshed gears.
As the gears rotate they separate on the intake side of the pump, creating a void and suction which is filled by fluid. The fluid is carried by the gears to the discharge side of the pump, where the meshing of the gears displaces the fluid. The mechanical clearances are typically small—on the order of 10 μm. Such tight clearances, along with the gears' speed of rotation, effectively prevent the fluid from leaking backwards. The rigid design of the gears and the pump housing allow for very high pressures and the ability to pump highly viscous fluids.
There are two main variations of gear pumps: external gear pumps, which use two meshed external spur gears, and internal gear pumps, which use an external gear rotating inside an internal spur gear. Both external and internal gear pumps are widely used in motor vehicles to pump lubricating oil to vital powertrain components. During operation, gear pumps typically generate various noises.